Process for treatment of coiled aluminum sheet

ABSTRACT

Damage to rolls in aluminum cold rolling mills is inhibited by a steam treatment applied to the lateral edges of coiled aluminum sheet as it emerges hot from the hot rolling mill.

United States Patent Anderson et al.

[ Dec. 30, 1975 [S4] PROCESS FOR TREATMENT OF COILED ALUMINUM SHEET [75] Inventors: Arvid N. Anderson; Wayne W.

Binger, both of New Kensington, Pa.

[73] Assignee: Aluminum Company of America, Pittsburgh, Pa.

[22] Filed: Feb. 27, 1975 211 Appl. No.: 553,67:

[52] U.S. Cl 72/202; 148/11.5 A [51] Int. Cl. B21B 45/02; 8210 31/00 [58] Field of Search 72/200, 201, 202, 342, 72/364, 700; 148/115 A, 16, 13, 20.3; 242178.]; 266/4 S, 6 S

[56] References Cited UNITED STATES PATENTS 2,088,241 7/1937 Irvin 72/202 ROLL/N6 g mu. 42

2,409,384 10/1946 Peterson 148/13 R FOREIGN PATENTS 0R APPLICATIONS 21,806 6/1972 Japan 72/200 OTHER PUBLICATIONS Heat Treatment in Steam, B. R. Swann, "Metal Treatment and Drop Forging," Apr. 1954, pp. 167472.

Primary Examiner-C. W. Lanham Assistant ExaminerE. M. Combs Attorney, Agent, or Firm-John P. Taylor, Esq.

[57] ABSTRACT Damage to rolls in aluminum cold rolling mills is inhibited by a steam treatment applied to the lateral edges of coiled aluminum sheet as it emerges hot from the hot rolling mill.

7 Claims, 1 Drawing Figure GENERITOR U.S. Patent Dec. 30, 1975 3,928,999

COL D ROLL/N6 M/LL STEA M GENE/7A r01? HOT ROLL/N6 MILL PROCESS FOR TREATMENT OF COILED ALUMINUM SHEET BACKGROUND OF THE INVENTION This invention relates to treatment of hot aluminum sheet. More particularly, this invention relates to steam treatment of the lateral edges of coils of hot aluminum sheet to inhibit subsequent damage to rolls in a cold rolling mill.

Increasing production demands and efficiencies have created a need for increasing the output of aluminum coiled sheet from hot rolling mills. As rolling velocity and/or metal reduction has increased in the hot rolling mill in response to this need, higher coiling temperatures have resulted. With the adoption of such practices, it has been noted that the subsequent working of such sheet in a cold rolling mill results in damage to the rolls, especially that portion of the roll near the width extremities of the sheet. The particular damage appears to be one of detrimental burnishing of the work rolls which in turn mars subsequent aluminum sheet passed thcrethrough and causes the work rolls to be more likely to crack and spall.

While it is not fully understood what has occurred, apparently the occurrence of such higher coiling temperature in the hot rolling mill causes an alteration of the characteristics of the aluminumsheet so as to result in this subsequent damage to the rolls in the cold rolling mill.

The rolling of the aluminum sheet in the hot rolling mill includes the use of coolants containing over 90% water. Due to the temperatures encountered in the hot rolling mill, much of this water is volatilized and the mill is often engulfed with steam. Yet, apparently this has little or no effect upon the conditions occurring in the aluminum sheet at this temperature which causes the subsequent damage alluded to above.

It was quite surprising therefore to discover that if the aluminum sheet emerging from the hot rolling mill was coiled and the lateral edges or sheared faces of the coil subjected to a spray of ordinary steam, subsequent damage to the rolls in the cold rolling mills is either mitigated or eliminated completely.

SUMMARY OF THE INVENTION In accordance with the invention, therefore, damage to the rolls of a cold rolling mill is inhibited by the coiling of the hot aluminum sheet and thereafter subjecting the lateral edges of the coiled aluminum sheet to a spray of steam while the coil is still hot.

BRIEF DESCRIPTION OF THE DRAWING The sole drawing of the invention is a schematic illustration of the invention.

DESCRIPTION OF THE INVENTION Referring now to FIG. 1, it can be seen that a sheet of aluminum emerges from hot rolling mill l and moves to station 20 as a hot coil 30. It should be noted that the use of the term aluminum" herein is intended to refer to aluminum or alloys wherein at least 50% by weight of the metal is aluminum. While in this coiled form, a spray of steam is applied to each of the lateral edges or sheared faces 32 and 32' of the aluminum coil via steam nozzles 42 and 42' from a steam generator 40. The steam is an ordinary atmospheric pressure steam having a temperature of approximately lO0C. Steam 2 generator 40 itself may be any conventional boiler capable of providing a sufficient amount of steam. For example, it has been found that for a coil of about 8-foot outer diameter and 2-foot inner diameter approximately 9 pounds of water per minute will be needed in the form of steam at 100C.

After treatment for about Iminute with the steam, the coil is further annealed if desired and then moved to a cold rolling mill and then treated conventionally in the cold mill operation. It should be noted here that the treatment must be in the form of steam, not water, since water droplets as a ,moisture source have been found to produce, in the subsequent cold rolling, an extremely burnished condition on the rolls. Furthermore, while the steam is preferentially directed against the sheared faces of the coils, the beneficial effects can be demonstrated simply by exposing'the coil faces to a cloud of steam. However, the hotter the coil, the more advantageous it has been found to be to direct the steam directly toward the sheared faces or lateral edges.

The treatment of the hot coil with steam must be made within about 30 minutes of the initial emergence of the coil from the hot rolling mill. Furthermore, the

coiling temperature must be at a certain minimum temperature range before detrimental burnishing is observed on a cold mill. This coiling temperature range may vary with particular aluminum alloys. For example, it has been found with Aluminum Association Alloy No. 3004 that the detrimental burnishing does not occur until the coiling temperature reaches a minimum range of about 450-550F (about 232-288C). On the other hand, detrimental burnishing does not occur with Aluminum Association Alloy Nos. 5082 or 5182 until the coiling temperature reaches a range of about 600-650F (about 3l5-343C).

It should be noted that when batches of coils at or near this temperature range are subjected to this treatment, no harmful effects have been noted when all the coils are so treated even though some of the coils may be cool enough to not absolutely require the treatment. In fact, the employment of such a treatment even at lower temperatures has been postulated to be sufficiently beneficial to permit the use of an air anneal instead of a controlled atmosphere anneal, thus eliminating the need for an inert or reducing atmosphere which in some instances requires consumption of addi tional amounts of natural gas.

The discussion of a minimum range in which the treatment should be applied, rather than a fixed minimum figure, is necessitated because the burnishing damage which will occur if the treatment is omitted is one of degree, there being no sharp cut-off temperature demarcating whether detrimental burnishing will occur. Thus one should be alerted, when operating within this range or above, that the possibility of detrimental roll burnishing exists and will increase with rising temperature.

It has further been found that, for any particular alloy, there is a temperature above which the steam treatment will not be beneficial unless it is applied promptly, that is, within about the first 5 minutes and preferably the first 2 minutes after coiling. For example, in the case of Aluminum Association Alloy No. 3004, if the temperature exceeds about 300C the steam treatment must be applied immediately, i.e. within about 25 minutes of the initial emergence of the coil from the hot rolling mill.

Following treatment in station 20, the coil is transported to either an annealing furnace (not shown) or to a cold rolling mill 50 in which it is conventionally processed. When aluminum sheet is exposed to the high coiling temperatures previously referred to in the hot rolling mill, and then subsequently, in accordance -with the invention, subjected to the steam treatment while in coiled form, it has been found that roll burnishing in the cold rolling mill is practically eliminated.

To further illustrate the invention, the following tests were conducted:

EXAMPLE I Twenty coils of Aluminum ,Association Alloy No. 3004, each having an outer diameter of 8 feet and an inner diameter of 2 feet, were processed through a hot rolling mill with exit temperatures ranging from 460-565F, and averaging about 530F. Each coil was sprayed for l minute on one sheared face or lateral edge with steam from a portable steam generator. The untreated face acted as a test control. The temperature drop due to the spraying and natural cooling during the 1-minute spray treatment was measured and found to be an average of about 3F.

The coils were then annealed by bringing the metal temperature up to 650F. The coils were then cooled to room temperature and then cold rolled. After all the coils were cold rolled, the work rolls were examined for damage. No roll burnishing was evident on the work rolls on either end, i.e. both treated and untreated sides. A second series of coils at the same average exit temperature from the hot rolling mill were then similarly processed without the steam treatment. Upon cold rolling, burnishing of the work rolls was evident. Thus, the beneficial effect of the steam treatment was evident even when the steam was not directed to both faces or lateral edges of the coil.

EXAMPLE II A series of 44 coils of Aluminum Association Alloy No. 3004, having the same outer diameters and inner diameters as in Example l, were hot rolled resulting in coil exit temperatures of 540-6l0F with an averageof about 580F. The lateral edges of each of the coils were steamed as in Example I within about -30 minutes after exit from the hot rolling mill. The coils were then subjected to the same annealing treatment as in Examplc I and cold rolled. In this instance, the burnishing of the work rolls after all the coils were cold rolled was evident, indicating that the steam treatment was not effective for these coils, apparently due to the higher exit temperature of the coils from the hot rolling mill.

EXAMPLE Ill The processing of Example II was repeated with a third group of 38 coils having an average coil exit tem- 4 perature of 622F with the exception that one lateral edge of the coils was steamed for L5 minutes within 2 minutes after exiting from the hot rolling mill. After identical annealing treatment and subsequent cold rolling, it was noted that no burnishing of the work rolls was evident on the treated side but burnishing was evident on the untreated side thus indicating that the steam treatment is effective at temperatures of 575F or higher for Aluminum Association Alloy No. 3004 if the treatment is applied immediately after exiting of the coiled aluminum from the hot rolling mill, i.e. within about 2-5 minutes. i

What is claimed is:

l. A process for inhibiting damage to rolls in a mill for cold rolling aluminum sheet which comprises:

a. coiling the aluminum sheet as it exits from a hot rolling mill; and

b. thereafter applying a spray of steam to the lateral edges of said coiled sheet prior to its entry into the cold rdlling mill.

2. The process of claim I wherein when the coil leaves the hot rolling mill at or above a predetermined minimum temperature range said predetermined minimum temperature range being alloy dependent, said steam is sprayed onto said coil within a sufficiently short period of time after the exit of said coiled sheet from said hot rolling mill so as to provide the desired inhibition of damage to the work rolls of the cold rolling mill.

3. The process of claim I wherein the temperature of said coiled sheet is determined and said steam spray is applied directly to the lateral edges of said coil within 5 minutes of the exit of said coil from the hot rolling mill if said coil temperature exceeds a predetermined minimum temperature for that alloy.

4. A process for inhibiting damage to rolls in a mill for cold rolling aluminum sheet which comprises:

a. coilingfa hotsheet of aluminum issuing from a hot rolling mill; and thereafter b. applyinga spray of steam to the lateral edges of said coiled sheet prior to its entry into the cold rolling mill and'before the coil temperature has dropped below about 275C.

5. The process of claim 4 wherein said steam spray is applied within 30 minutes of the coiling of the aluminum sheet. i

6. The process of claim 4 wherein the temperature of said coiled aluminum sheet is measured immediately after coiling, and said steam spray is applied directly to the lateral edges of the coil within 5 minutes of said coiling if the temperature of said coil exceeds a predetermined minimum coil temperature.

7. The process ofclaim 6 wherein said predetermined minimum temperature is about 300C.

is a a a: 4 

1. A PROCESS FOR INHIBITING DAMAGE TO ROLLS IN A MILL FOR COLD ROLLING ALUMINUM SHEET WHICH COMPRISES: A. COILING THE ALUMINUM SHEET AS IT EXITS FROM A HOT ROLLING MILL; AND B. THEREAFTER APPLYING A SPRAY OF STEAM TO THE LATERAL EDGES OF SAID COILED SHEET PRIOR TO ITS ENTRY INTO THE COLD ROLLING MILL.
 2. The process of claim 1 wherein when the coil leaves the hot rolling mill at or above a predetermined minimum temperature range said predetermined minimum temperature range being alloy dependent, said steam is sprayed onto said coil within a sufficiently short period of time after the exit of said coiled sheet from said hot rolling mill so as to provide the desired inhibition of damage to the work rolls of the cold rolling mill.
 3. The process of claim 1 wherein the temperature of said coiled sheet is deteRmined and said steam spray is applied directly to the lateral edges of said coil within 5 minutes of the exit of said coil from the hot rolling mill if said coil temperature exceeds a predetermined minimum temperature for that alloy.
 4. A process for inhibiting damage to rolls in a mill for cold rolling aluminum sheet which comprises: a. coiling a hot sheet of aluminum issuing from a hot rolling mill; and thereafter b. applying a spray of steam to the lateral edges of said coiled sheet prior to its entry into the cold rolling mill and before the coil temperature has dropped below about 275*C.
 5. The process of claim 4 wherein said steam spray is applied within 30 minutes of the coiling of the aluminum sheet.
 6. The process of claim 4 wherein the temperature of said coiled aluminum sheet is measured immediately after coiling, and said steam spray is applied directly to the lateral edges of the coil within 5 minutes of said coiling if the temperature of said coil exceeds a predetermined minimum coil temperature.
 7. The process of claim 6 wherein said predetermined minimum temperature is about 300*C. 